Assessing Camelina sativa as a fallow replacement crop in wheat production systems

Abstract

Emerging sustainability issues with summer-fallow period has prompted producers to identify fallow replacement crops in wheat (Triticum aestivum) production systems. Camelina [Camelina sativa (L.) Crantz] has been identified as a potential fallow replacement crop in the semiarid Great Plains. Camelina has uses in animal and human nutrition, biofuel production, and bio-based products. Three field experiments were conducted to develop production recommendations for camelina in wheat production systems in the semiarid Great Plains. In the first study, three camelina cultivars were evaluated in mid-March (March 17, 2014; March 18, 2015), early-April (April 3, 2013; April 1, 2014 and 2015), and mid-April (April 16, 2013; April 15, 2014 and 2015) at Hays, KS. Findings from this study showed delaying camelina planting until early- or mid-April resulted in 34% increase in seed yield. Planting date affected oil concentration, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and linolenic acid concentration. The concentrations of SFA, MUFA, PUFA, linoleic acid, and linolenic acid were also different among cultivars. A second study was conducted to evaluate the response of camelina to nitrogen (N), and sulfur (S) fertilizer application. Nitrogen rates (0, 22, 45 and 90 kg ha⁻¹), and S rates (0 and 20 kg ha⁻¹) were applied in a randomized complete block design with a split-plot arrangement. The main plots were S application rates and the subplot factor was N rates. Sulfur application did not affect seed yield, oil, protein, or seed nutrient concentration. The agronomic optimum N rate was 49 kg N ha⁻¹, however, the economic optimum N rate ranged from 25 to 31 kg N ha⁻¹ based on current N fertilizer cost, and camelina seed price. Nitrogen application had no effect on SFA, MUFA, and PUFA. Moderate N application increased seed calcium (Ca) concentration, whereas higher N rate increased zinc (Zn), and manganese (Mn) concentration in the seed. There was a general negative relation between N application with copper (Cu), and molybdenum (Mo) in camelina seed. Our study shows that camelina needed to be applied with a minimum of 25 kg N ha⁻¹ for optimum production. A third study investigated effects of crop rotation on crop yield, soil water, soil CO₂ flux, and soil health in wheat-camelina rotation systems. Rotation systems in this study were wheat-fallow (W-F), wheat-sorghum (Sorghum bicolor) -fallow (W-S-F), wheat-spring camelina (W-SC), and wheat-sorghum-spring camelina (W-S-SC). Crop rotation had no effect on sorghum grain yield. However, winter wheat yield decreased by 15% when fallow was replaced by camelina in the rotation system. Camelina yield in W-SC was 2-fold greater than that in W-S-SC. Soil water content in the more intensified rotations were less than rotations with fallow, irrespective of sampling period. Soil pH, phosphorus (P), and total nitrogen (TN) were not different among rotation systems. Nonetheless, soil profile N, soil organic carbon (SOC), microbial biomass carbon and N (MBC and MBN), and potentially mineralizable nitrogen (PMN) were different among rotation systems. Soil particle aggregation increased with increasing cropping intensity. This suggests improved soil structure with cropping intensification.